The treads of modern tires must meet performance standards which require a broad range of desirable properties. Thus, rubber compositions suitable for tire treads should exhibit not only desirable strength and elongation, particularly at high temperatures, but also good cracking resistance, good abrasion resistance, desirable skid resistance and low tan delta values at low frequencies for desirable rolling resistance. Additionally, a high complex dynamic modulus is necessary for maneuverability and steering control.
It has long been recognized that rubber compositions composed of rubber, curative and carbon black alone possessed too high a Mooney viscosity to be reasonably processed into tire tread compositions. Accordingly, it has become conventional in several applications to extend the rubber with an aromatic oil prior to processing, thereby reducing the Mooney viscosity of the rubber composition to a readily processable degree.
However, the incorporation of excessive amounts of such oil has been found to adversely affect the tensile properties, especially the tensile strength and modulus, of the resulting composition. Thus, it would be desirable to possess a processing aid which would increase the processability of a tire tread composition and which would not adversely affect the tensile properties of the cured composition.
Accordingly, it is an object of this invention to provide a tire having a tread composed of a composition which is readily processed.
It is a further object of this invention to provide a tire having a readily processed tread exhibiting improved rolling resistance.
It is yet another object of this invention to provide a readily processed tire having a tread having an improved flexural modulus.
These objects, and other additional objects will become more apparent from the following description and accompanying Examples.